[hypoxia]

The Allison shop that replaced my Allison 4000 transmission advised me that the old style TCM is guaranteed to fail.  I took that advice and had them replace it.  Apparently the bonding material between the connector and the body of the TCM fails which causes broken connections internally.  That's the way I understood it.  This place is busy with tow trucks dragging in every kind of truck and busses all day and night.  They had TCM's everywhere I looked and said they commonly replace a dozen a day.

If you have that TCM you may want consider that and do your research.
 
Atlantic Detroit Diesel-Allison, Middletown, CT